#include<iostream>
#include<string>
#include <math.h>
using namespace std;


double& f( double x ) 
{
static double y;
y = sin(x);
return y;
}

int main()
{
	double a = 3.14/6;
	double y;
	y = f( a );
	cout << "y = " << y << endl;
	return 0;
}

